The FN+F9 keys are the hot keys to toggle the keyboard backlight on/off. If you turn it on, the backlight should come on and after about 30 seconds of non-use the keyboard light will turn off. Pressing any key should bring the light back on. If this is not working please contact Acer support for your location from this link:

The models that sold in the US have a backlit keyboard. No driver is needed in order for it to work. Please contact the Acer support channel for your country from the link below, so they can verify whether these models sold in Hong Kong have a backlit keyboard.

Yes you are right. I cannot find any models in hk with backlit keyboard in fact there's no choice at all. It is therefore quite annoying that they use it the same advertisement as the US which shows backlit keyboard as major selling point on their website